Method of electroplating zinc on cadmium zinc alloys



April 28, .1936. E. c. DQMM 2&038551 METHOD OF ELECTROPLATING ZINC ONCADMIUM ZINC ALLOYS Filed oct. 51, 1954 Patented Apr. 28,l 1936 UNITED-STATES METHOD OF ELECTROPLATING ZINC 0N CADMIUM. ZINC ALLOYS CarletonDomm7 Niles, Mich., assignor to National-Standard Company, Niles, Mich.,a corporation of Michigan Application october 31,1934, serial No,'150,875

8 Claims.

This invention relates to improvements in a method of coating metal. u 4

This application is a continuation in part of my co-pending applicationSerial No. 653,549, filed January 25, 1933.

In the Crapo Patent No. 1,984,335, is described a method of coating aferrous article by hotgalvanizing it with zinc, and over that depositinglziiy some other method an additional coating of It has now beendiscovered that in those methods the thickness of the undercoating maybe decreased without injuring corrosion-resistance to the type ofcorrosion of which salt-spray is typical, if insteadof thezinc-undercoating an alloy of cadmium and zinc is used for such undercoating. At the same time, such an alloy may be applied at a lowertemperature, and thus may be used in certain instances where theapplication of zinc alone by the hot-dip method might interfere with thecharacter of the base.

The invention is particularly applicable to coat- `ing strands of wireto be used in reinforcing the bead of a tire. The wire when so usedcommonly acts as a tension-member, and is imbedded in a rubber or rubbercompound. When -so used, the wire is exposed to corrosive 'and rustingagents, ltiiarticularly to moisture which may seep into the The drawingshows in 'diagrammatic form an embodiment of my invention.4

In accordance with the invention, a metal, for example wire suitable'for use in tire beads, is first hot-dipped to provide 'a coating of acadmium-zinc alloy.: This may be done, for example, by dipping the wirein a hot molten alloy of zinc and-cadmium., Such an alloy always has amelting point lower than that. of zinc, and certain of the alloys have amelting point below that of either zinc or cadmium.

A coating of zinc is then put over the rst coat by electrolysis orelectroplating. Not only does a double coating applied by the abovementioned method give very good corrosion-resistance, but it has beendiscovered that the electro-coat tends to fill in the depressions in thelower zinc-cadmium alloy coat and thus produce a uniform and smoothcoating. A coatingof the order of thickness of the lower coat ispreferred.

If desired, copper or other suitable material may be applied over thecorrosive-resistant double coating in order to increase the adhesivenessof the wire to rubber. It is frequently desirablel to apply such acoating when wire is used as a reinforcement for a tire bead.

The new process herein described is especially useful in procuring acoating of a desired and uniform thickness. Inlpractice, the wire isgiven a hot coat rst, and preferably I wipe this thin. In the nextstage, the coating is put on by electroplating; the operation can becontinued to give exactly a desired thickness. At the same time, thecoating acquires a smooth, uniform character which is freefrom holes,defects, and the like.

As an example of the invention, it is preferred The foregoingdescription has been given for.l clearness of understanding only, and nounnecessary limitations should be understood therefrom. but the appendedclaims should be construed as broadly as permissible in view of theprior art.

What I-regard as new and desire to secure by Letters Patent is:

1, The process of coating a ferrous article which comprises applying toit by the hot-dip process a coating of an alloy of cadmium and zinc, andeiectrodepositing thereon an outer coating of zinc.

2. The method ofcoating a metal to increase its corrosion-resistancecomprising nrst applying to it a molten zinc-cadmium alloy, and thenapplying 'a second coating of zinc over the first coating.'

3. The method of producing a ferrous tire-bead reinforcement wire whichcomprises nrst coating a ferrous wire with a zinc-cadmium alloy by thehot-dip process, andthen electroplating zinc over the hot-dipped wire toproduce a uniform coating of desired thickness.

4. The method as set forth the zinc-cadmium alloy contains approximately80 parts of zinc to 20 parts of. cadmium.

5. A coated ferrous article, comprising a. ferrous base having ahot-dipped coating of a zine.

cadmium alloy thereon, and over that an electrodeposlted coatingsubstantially wholly Yof zinc.

6. A coated ferrous wire comprising a ferrous base wire having ahot-dipped coating of a cadmium-zinc alloy thereon, and over that anelectrodeposited coating substantially wholly of zinc.'

7. A coated tire bead wire comprising a ferrous base wire having ahot-dipped coating of a zincn coating substantially wholly of zincthereon, and having a coating of rubber vulcanized thereto.

8. An article as set forth in claim 5, in which the zinc-cadmium alloycontains approximately 80 parts zinc to 20 parts cadmium. v

Enom cARLm'oN Dorm.

in claim 1, in whichl Y cadmium alloy thereon, and electrodepositedl

